Under the hot summer sun of the San Joaquin Valley, just south of Merced, Miguel Guerrero of The Wine Group is trying a new high-wire act. In collaboration with University of California-Davis Cooperative Extension, Roduner Ranch vineyard manager Guerrero is experimenting with Cabernet Sauvignon vines and other varieties elevated by a single wire at 66 inches – plantings that are 2-3 feet higher than the traditional winegrape canopy.